later, at the pentagon he offered hope following a ceremony remembering those killed when a hijacked plane targeted the building. >> no single event can ever destroy who we are. no act of terrorism can ever change what we stand for. >> reporter: those same themes of courage rang out near shanksville, pennsylvania, where a plane crashed while passengers fought to keep it from reaching the capitol. >> have not forgotten the heroism of your husbands, wives, sons, daughters, mothers, fathers. >> so many lost fighting for a country they believed in. and despite the pain, there are signs of healing. for instance, the new world trade tower rising behind me is set to be complete in just over a year. and for many, it's a sign that this city is now trying to move on. reporting live in lower manhattan, i'm daniellelee, nbc news. >> it's a day americans won't forget. coming up, a big change to a bay area tech heavyweight.